Study on Whale Stranding, Sonar Is Inconclusive
Thursday, March 30, 2006
Federal ocean scientists said yesterday they were unable to determine whether Navy sonar caused a mass stranding of whales on the North Carolina shore last year.
In their report on the stranding -- one of the largest and most troubling in two decades -- the National Marine Fisheries Service researchers concluded that Navy ships had used sonar in the area the day before the whales came onshore. But detailed necropsies and analyses did not find any physical signs of a connection between the loud sonar pings and the whales' rush to shore.
"Experts from around the country worked on these samples and tests, and the bottom line is that we are not able to reach a definitive cause for the stranding," said Aleta Hohn, the Fisheries Service's lead scientist on the report.
The report concluded that most of the animals were otherwise healthy. In all, 33 pilot whales, two pygmy sperm whales and a minke whale stranded and died within two days. Strandings of more than one species at a time are rare.
The report on the January 2005 stranding had been anxiously awaited by the Navy and environmentalists because the animals died near the proposed site of a 660-square-mile underwater sonar testing range.
The Navy has said the sonar range is essential to train sailors and will not be a danger to the many whales in the area. Some environmentalists disagree, saying that the growing number of strandings around the world linked to naval active sonar make the range -- which is near a major whale migration path -- a threat to animals.
The two sides, which are battling in court over sonar, interpreted the report differently. "The NOAA report clearly acknowledges that there is no pathology implicating sonar as a cause of the stranding," said James A. Symonds, director of the Navy's environmental programs.
"We believe the time frame and the distance at which active sonar was used, two to three days prior to the stranding and over 50 nautical miles from [the site of the stranding] make it extremely unlikely that our sonar affected the animals in any way," he said.
Michael Jasny of the Natural Resources Defense Council disagreed. "Today's report by the federal government establishes that sonar was a possible cause of the January 2005 mass stranding," he said. "It confirms that the event itself was highly unusual, being the only mass stranding of offshore species ever to have been reported in the region; and that it shared 'a number of features' with other sonar-related mass stranding events."
Navies worldwide have been using powerful mid-frequency sonar for years, but the link to whale strandings is quite recent. The U.S. Navy acknowledged that its sonar caused a mass stranding in the Bahamas in 2001, and numerous other suspected cases have been reported. Most recently, Spanish officials concluded that beaked whales that came ashore along the Costa del Sol most likely did so because of naval sonar.
Fisheries Service acoustics specialist Brandon Southall said the amount of sonar used in the area prior to the North Carolina stranding was not unusual. But he said it was impossible to say whether the sonar led to the strandings.